Compact vacuum insulation embodiments

ABSTRACT

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially &#34;point&#34; or &#34;line&#34; contacts with the metal wall sheets. In the case of monolithic spacers that form &#34;line&#34; contacts, two such spacers with the line contacts running perpendicular to each other form effectively &#34;point&#34; contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

The U.S. Government has rights in this invention under Contract No.DE-AC02-83CH10093 between the U.S. Department of Energy and the SolarEnergy Research Institute, a Division of Midwest Research Institute.

CROSS REFERENCE TO RELATED APPLICATION

This patent application is a divisional application of U.S. patentapplication, Ser. No. 181,926, filed Apr. 15, 1988, entitled CompactVacuum Insulation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to insulation panels, andmore specifically to vacuum insulation panels that have a high degree ofresistance to heat transfer and are thin and bendable to form curvedinsulation panels, applications of such panels, and methods of makingsame.

2. Description of the Prior Art

There is nothing new about insulation or in the use of vacuum panels forinsulation. There is, however, a rapidly emerging need for much improvedinsulation in terms of a combination of better insulation effectiveness,lighter weight, thinner, more durable, and more bendable or formableinsulation products. The needs for such better insulation productsemanate from such diverse areas as space-related vehicles and equipment,extremely low-temperature cryogenic vessels and pipes in scientific andindustrial applications, and even common household appliances. Forexample, space vehicles and equipment to be launched into space need avery high quality of insulation to protect humans and equipment, yetthere is no room for typically bulky insulated walls and panels.

State-of-the-art insulation for cryogenic applications is complex andexpensive and still has significant shortcomings. For example, aninsulation structure known as "cryopumped insulation" is often used forinsulating cryogenic vessels and pipes. Such cryopumped insulationcomprises many laminated layers of impervious material sealed at theedges and positioned adjacent the cryogenic material; e.g., liquidnitrogen. The liquid nitrogen is so cold that it causes the air inadjacent sealed spaces between the laminated sheets to liquify, thusleaving a partial vacuum in the spaces. This air-liquifying phenomenonoccurs through adjacent layers a sufficient depth into the laminatedinsulation structure such that heat transfer is inhibited by theadjacent vacuum layers created or "cryopumped" in the insulationstructures.

While such "cryopumped" insulation works quite well at the extremely lowtemperatures of cryogenic materials, like liquid nitrogen, which arecold enough to liquify air, it does not insulate at all in normaltemperature ranges. Also, such "cryopumped" insulation is relativelythick and bulky, typically requiring several inches of thickness to beeffective, and it is expensive and difficult to form into desired shapesor contours. Yet, prior to this invention, there were no thin,non-bulky, formable, yet equally effective alternatives.

On the domestic scene, both consumers and governments are demanding thatmanufacturers of home appliances, such as refrigerators, water heatersdishwashers, washing machines, clothes dryers, and the like, make theseappliances much more energy efficient. For example, the CaliforniaEnergy Commission has mandated a 50% reduction in the energy use ofrefrigerator/freezers to be sold in that state in 1992. That mandatedreduction in energy usage, while maintaining current dimensions, is notachievable without significant improvement in side-wall thermalefficiencies. Current technology could accommodate the reduction in heattransfer through the side walls of appliances by making insulated wallpanels three times as thick. However, people do not want refrigeratorswith walls a foot thick. Architectural designs of homes and apartments,door widths, and the like practically prohibit increasing externaldimensions of home appliances, and decreasing useable interior spacewill meet with much consumer dissatisfaction and resistance.

Thinner insulation panels that improve insulating effectiveness wouldsolve these problems, but ultra-thin, highly effective, and long-lastinginsulation panels are not easy to make. In fact, prior to thisinvention, each of these criteria, i.e., ultra-thin, highly effective,and long-lasting, has been mutually exclusive of at least one of theothers.

There have been some notable attempts prior to this invention to improveinsulation effectiveness with somewhat thinner panels. For example, U.S.Pat. No. 2,989,156, issued to F. Brooks et al., discloses an insulationpanel comprising an evacuated space between metal sheets, whichevacuated space is filled with perlite powder. U.S. Pat. No. 3,151,365,issued to P. Glaser et al., shows the use of a mixture of fine carbonblack particles and other fine particles filling an evacuated, enclosedstructure, intermediate foil radiation shields, and anemissivity-reducing coating of silver. The H. Strong et al., patent,U.S. Pat. No. 3,179,549, uses a mat of very fine, oriented glass fiberssealed inside an evacuated, welded metal envelope. The vacuum used isonly about 10⁻⁴ atmospheres (10⁻² Torr), and it requires a fiber mat ofsufficient density and thickness to be opaque to thermal infraredradiation. U.S. Pat. No. 4,444,821, issued to J. Young et al., alsodiscloses an evacuated panel filled with a glass fiber mat with plasticedge seal strips and a gettering material positioned in the evacuatedchamber. This panel also specifies only a low-grade vacuum of about 10⁻²Torr. The N. Kobayashi patent, U.S. Pat. No. 4,486,482, also uses aglass fiber mat inside a vacuum envelope made of welded stainless steelsheets. This glass mat is stitched with glass fibers that runperpendicular to the plane of the mat and are supposed to support theexternal atmospheric pressure load on the panel walls to keep them fromcollapsing.

The above-described prior art vacuum panels are no doubt more effectivethan conventional foam and fiberglass insulation panels. However,constructing a truly effective and long-lasting insulation panel is noteasy and is not achieved by these prior art structures to the extentnecessary to meet the needs described above. For example, the low-gradevacuums used in the prior art patents cannot achieve insulationefficiencies high enough for use in ultra-thin panels. Plastic edgeseals cannot maintain a vacuum over an extended period of time, and theyreally cannot withstand high-temperature exposure or solar radiationexposure without serious degradation and outgassing. Metal envelopeswith welded seams will hold the required vacuum, but it is virtuallyimpossible to achieve the perfectly leak-free welds required formaintaining very high-grade vacuums over many years, when such weldshave to be made in the presence of the billions of microscopically fineglass fibers and perlite particles used in prior art panels. A singleparticle or fiber intruding into the weld area could create amicroscopic leak that would be very difficult to detect, but wouldnever-the-less seriously compromise the lifetime of the vacuum insidethe sealed insulation panel, thus compromising the usefulness of thepanel.

The use of a vacuum results in the need for a sufficient structureinside the panel to hold the opposite panel walls from collapsingtogether. The glass fiber mats and perlite powders used in the prior artpanels described above can serve that function. However, in high-ordervacuums the inwardly directed sidewall pressures become very great sothat such fiber mats and powders become more tightly compacted, thusoffering more direct heat conduction paths through the insulation panelthan desired. Also, to be really adaptable for a wide variety of uses,the insulation panel should be bendable around curves. However, bendingthe prior art panels would almost certainly crimp one wall sheet of thepanel into the other, thereby forming a "cold short" where one wall orsheet touches the other. Even if the glass fiber mats of the prior artwould physically hold the two opposite sheets apart, the mat itselfwould be so compressed at the crimp or bend that it would virtually formthe cold short itself.

The laser-sealed vacuum insulating window invented by David K. Benson,one of the joint inventors of this invention, and C. Edwin Tracy, nowU.S. Pat. No. 4,683,154, solved the problem of long-term sealing andstructural support against collapse or cold short by laser-welding glassspacer beads between two glass sheets. However, that structure is quitethick, heavy, and fragile, being made with glass, and it is rigid, so itcannot be bent around curves. Therefore, while it is a highly efficientinsulation panel, its utility is limited.

SUMMARY OF THE INVENTION

Accordingly, a general object of the present invention is to provide ahighly effective, ultra-thin insulation panel.

Another object of the this invention is to provide a highly effective,ultra-thin insulation panel that is durable, resistant to degradation,e.g., by high temperatures, corrosive fluids, and sunlight, and that islong-lasting and bendable without damage or significant loss ofinsulating capability.

A more specific object of this invention is to provide a highlyeffective, ultra-thin insulation panel that has superiormanufacturability, thus more consistent, dependable quality at areasonable cost.

A more specific object of this invention is to provide a monolithic, yetvery effective glass or ceramic spacer for use alone or in combinationwith additional similar glass or ceramic spacers in a high-gradeevacuated chamber between two rigid, yet bendable metal sheets formingan insulation panel, which is easy to manufacture and use.

Another specific object of this invention is to provide a plurality ofdiscrete glass or ceramic spacers between side sheets that form a vacuumchamber at predetermined spatial relationships to each other and amethod of positioning such discrete spacers during assembly.

Additional objects, advantages, and novel features of the invention areset forth in part in the description that follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing specification or may be learned by the practice of theinvention. The objects and advantages of the invention may be realizedand attained by means of the instrumentalities, combinations, andmethods particularly pointed out in the appended claims.

To achieve the foregoing and other objects and in accordance with thepurposes of the present invention, as embodied and broadly describedherein, the article and apparatus of this invention may comprise twoadjacent metal sheets spaced closely together with a plurality ofspherical glass or ceramic beads or other discrete shapes optimallypositioned between the sheets to provide mechanical support to maintainthe spacing therebetween while minimizing thermal conductance and sealedwith a metal weld around the edges. The glass beads or other shapes can,according to this invention, be formed in one or more monolithic sheetsand positioned between the metal sheets. One preferred form of suchmonolithic sheets includes a sheet of glass web with a plurality ofspherical nodules protruding in opposite directions from the web.Another preferred form includes a sheet of glass web with a plurality ofelongated ribs protruding in opposite directions from each side. Aplurality of such glass sheets can be laminated between the two outsidemetal sheets to further reduce linear heat conductance paths across thepanel. A similar effect can be obtained by providing the two outsidemetal sheets textured with ribs or convex protrusions with the twooutside sheets separated one from the other by a flat sheet of glasswebbing. Other specific embodiments of the invention include theinsulation panels configured in particular structures that enhancestrength and flexibility, as well as useful configurations forparticular purposes. Another structural embodiment includes a helicalwound glass or ceramic spacer bead that can be used to separate twoconcentric, cylindrical metallic sheets in the shape of a tubularconduit or pipe.

Further, the method of this invention includes using polystyrene-coatedbeads positioned in a jig, contacting the beads with one outer metalsheet heated enough to melt the polystyrene to adhere the beads to theone outer sheet and lifting them out of the jig, clamping the beadsbetween two outer metal sheets, heating to break down and outgas thepolystyrene and evacuating to the range of 10⁻⁶ Torr (10⁻⁸ atmosphere),and sealing by welding the seams around the edges of the outer metalsheets. One or more low-emissivity surface coatings can be used tominimize thermal infrared radiation, and a reactive metal getter isinstalled in the vacuum insulation to help maintain the vacuum.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specifications, illustrate the preferred embodiments of the presentinvention, and together with the description serve to explain theprinciples of the invention.

IN THE DRAWINGS

FIG. 1 is a perspective view of a segment of an insulation panelconstructed according to the present invention with a portion of theedge seam and one side wall cut away to reveal the spacer beadspositioned therein;

FIG. 2 is a cross-section of a preferred embodiment insulation panelaccording to the present invention;

FIG. 3 is a cross-section of a plurality of beads positioned in a jigprior to attachment of the beads to one of the exterior metal sheets ofan insulation panel according to this invention;

FIG. 4 is a cross-section of the assembly jig with the one outside sheetbeing attached to the beads on the jig;

FIG. 5 is a cross-sectional view of the jig similar to FIGS. 3 and 4,but with the beads attached to the outside sheet of the panel;

FIG. 6 is a cross-sectional view of an alternate embodiment of theinsulation panel according to this invention with a plurality of smallerbeads used as initial spacers for positioning the large beads;

FIG. 7 is a cross-sectional view of another embodiment of the presentinvention wherein the glass spacer beads are formed integrally with amonolithic spacer sheet;

FIG. 8 is a fragmented, exploded view of a panel assembly utilizing themonolithic spacer sheet of the embodiment FIG. 7;

FIG. 9 is a cross-sectional view of an embodiment similar to that shownin FIG. 7 and 8, but utilizing two of the monolithic spacer sheets;

FIG. 10 is a cross-sectional view of an insulation panel embodiment thathas a monolithic glass spacer comprising a web with a plurality ofnodules protruding from opposite sides with the nodules on one side ofthe web offset laterally from the nodules on the other side;

FIG. 11 is a perspective view of a portion of still another embodimentof the insulation panel according to the present invention with aportion of the edge seam and front panel and one of the monolithicspacer sheets cut away to reveal the complete structure, this embodimentof the monolithic spacer sheet having a plurality of elongated ribs,with the spacer sheets oriented so that the ribs of one spacer sheet runcross-wise to the ribs of the other;

FIG. 12 is a cross-sectional view of the insulation panel embodimentshown in FIG. 11;

FIG. 13 is a fragmentary, exploded view illustrating the assembly of theinsulation panel embodiment of FIGS. 10 and 12;

FIG. 14 is a graph illustrating effective heat transfer in relation tovacuum in the panel;

FIG. 15 is a cross-sectional view of a composite insulation panelcomprising of a plurality of the insulation panels described aboveimbedded in either a rigid or a flexible foam material;

FIG. 16 is a perspective view of a section of insulation panel accordingto this invention formed in a corrugated configuration;

FIG. 17 is a perspective view of a corrugated insulation section similarto that shown in FIG. 16, but further formed into a curved insulationpanel;

FIG. 18 is a cross-sectional view of an insulation panel according tothis invention formed into a cylinder with overlapping lateral edges;

FIG. 19 is a cross-sectional view of a composite insulation panelaccording to this invention formed as a rippled tube or conduit sectionthat is longitudinally expandable and contractable;

FIG. 20 is a cross-sectional view of the composite rippled tube orconduit section of FIG. 19 shown formed around a bend;

FIG. 21 illustrates in cross section a composite rippled tube or conduitsection similar to that shown in FIG. 19 used to connect together twoimmovable lengths of solid and unstretchable insulated pipes that may beformed according to embodiments of this invention;

FIG. 22 is a perspective view of a tubular insulated conduit accordingto this invention in which one or more helical glass spacers are used tohold apart two metallic tubular skin sections to form an insulated pipeor conduit;

FIG. 23 is a perspective view of an alternate embodiment of theinsulation panel according to the present invention in which the glassspacer is a flat web and the two metallic outer sheets are textured withribs running transverse to each other;

FIG. 24 is a perspective view of an alternate embodiment similar to thatin FIG. 23, but wherein the metallic outer sheets have protrudingnodules instead of ribs;

FIG. 25 is a cross-sectional view illustrating an application of theinsulation panel of the present invention for isolating thermal panewindows from a metal frame structure as well as for insulating againstheat transfer through solid structural members that support glazing orother building materials; and

FIG. 26 shows the insulated panel according to the present inventionformed as a press-on cap to block heat transfer through a window frameor other structural unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The ultra-thin insulation panel 10 embodiment according to thisinvention shown in FIG. 1 comprises of two outer sheets or walls 12, 14positioned in closely spaced-apart relation to each other. The seamsaround the edges of the panel where the two outer sheets or walls 12, 14meet are sealed, preferably by welding, as shown at 18. The interiorchamber 15 enclosed by the outer sheets or walls 12, 14 is evacuated toa high-grade vacuum in the range of at least 10⁻⁵ Torr, and preferablytot the range of 10⁻⁶ Torr. To hold this high-grade vacuum for manyyears, the edge seams 18 have to be sealed with almost perfectlyleak-proof quality.

When the chamber 15 is evacuated as described above, the atmosphericpressure on the outsides of the wall sheets 12, 14 would normallycollapse the wall sheets 12, 14 together, thereby causing a cold shortor direct thermal conduction path from one wall to the other across thepanel. To avoid such collapse, a plurality of discrete glass spacers,which can be in the form of spherical beads 16, are positioned optimallyto provide mechanical support to hold the two wall sheets 12, 14 apart,while minimizing thermal conductance. It is preferred that the metalwall sheets 12, 14 be formed of a low thermal conductivity metal such asstainless steel or titanium, both of which are easily weldable in avacuum and are sufficiently hard or rigid so that they do not formaround the spherical spacers, yet are bendable enough so the panel canbe formed in curves. Therefore, a near "point" contact is maintainedbetween each spherical glass bead spacer 16 and the metal wall sheets12, 14. For high-temperature applications, the beads 16 can be ceramicbeads instead of glass, so that they maintain their structuralintegrity, spherical shape, and near "point" contact with the metalwalls 12, 14. Therefore, while this discussion, specification, andclaims refer most often to the monolithic spacers as being glass, it isto be understood that ceramic spacer materials are also appropriateequivalents and are included within the scope of this invention.

Once the spacer beads 16 are properly positioned and the chamber 15 isevacuated, the atmospheric pressure on the outside surfaces of the wallsheets 12, 14 tightly squeezes or clamps the sheets 12, 14 against thebead spacers 16, thereby holding them in position. With proper spacingof the spacer beads 16, the insulation panel 10 can even be bent orformed around a curve, as shown in FIG. 1, and the spacer beads 16maintain the spacing between the wall sheets 12, 14 in the bend withoutcrimping or allowing a cold short between the two wall sheets 12, 14.

While there may be a number of ways to affix the spacer beads 16 inoptimum spaced relation to each other in the chamber 15, one preferredmethod of doing so is illustrated in FIGS. 3 through 5. Specifically,the spacer beads 16 are initially coated with a polystyrene or similaradhesive material. These polystyrene-coated beads 16 are then pouredonto the surface of a bead jig 52, which has a plurality of pockets 54formed in its surface with the proper spacing as desired for holding thespacer beads 16. One wall sheet 12 is heated and lowered into positionon top of the spacer beads 16 as shown in FIG. 4. The heat from the wallsheet 12 melts the polystyrene on the surface of the spacer beads 16 toadhere the beads 16 to the wall sheet 12 as shown at 20 in FIG. 4. Thewall sheet 12 is then allowed to cool, thereby allowing the polystyreneto cool and adhere the spacer beads 20 to the interior surface of thewall sheet 12. Once adhered, the wall sheet 12 can be lifted off the jig52, as shown in FIG. 5, with the beads 16 retained in proper position.Then, the other wall sheet 14 can be joined as shown in FIG. 2. With thetwo wall sheets 12, 14 clamped together and with the beads 16 in properposition, the assembly is then heated to a sufficient temperature tobreak down the polystyrene into more volatile styrene monomers, whichvaporize at such temperatures. The temperature should not be so high asto break down the polystyrene into its carbon elements, because thecarbon is higher in conductivity, and it has a higher infraredemissivity than desired. Under those temperature conditions, the chamber15 can be evacuated, and, while held under the vacuum, the edges 18 canbe welded to seal the vacuum in the chamber 15.

As mentioned above, other methods may also be used to secure the beadsin place while the clamping evacuation and weld sealing operations takeplace. For example, with ceramic beads 16 and titanium sheets 12, 14,the beads 16 may be positioned and maintained with proper spacingelectrostatically. Also, the beads may be held in proper position by ametal mesh until the outer wall sheets 12, 14 clamp them in place, orthey may be strung on wires or glass fibers.

The embodiment 40 shown in FIG. 6 is similar to that shown in FIGS. 1and 2 above, with the exception that the large spacer beads 16 arepositioned on the bottom wall sheet 14 and held in proper spacing by aplurality of smaller diameter beads 42. Again, once the top sheet 12 isclamped in position, the chamber 15 evacuated, and edges 18 welded shut,the spacer beads 16 will be held in position by the atmospheric pressureon the outside of the panel.

Another embodiment 60, as shown in FIG. 7, has the spacer beads 64formed as an integral part of a monolithic spacer sheet 62. Thismonolithic spacer sheet 62, which is also illustrated in FIG. 8, is oneunitary sheet of glass web 66 with a plurality of spherical nodules 64extending outwardly in both directions from the web 66. This monolithicspacer sheet 62 can merely be positioned on the bottom wall sheet 14,and then the top wall sheet 12 can be placed in position. Once thechamber 15 is evacuated and the edges 18 sealed, the spacer nodules orspheres 64 will be clamped into position by the atmospheric pressure.Therefore, it will not make any difference if the webbing breaks afterthe panel has been assembled. Consequently, after assembly, if it isdesired to bend the panel 60 around a curve, which would break the glassweb 66, the insulating quality and structural integrity and spacingbetween walls 12, 14 of the panel 60 itself will be maintained by thenodules 64.

The embodiment 68 shown in FIG. 9 is similar to that shown in FIGS. 7and 8, with the exception that two of the monolithic spacer sheets 62are utilized. The spacer sheets are positioned such that the nodules 64of one sheet 62 touch one outside wall sheet 12 and one side of the web66 of the adjacent panel on the other side. This embodiment defines amore tortuous path through a series of "point" contacts in which heatmust be conducted to make it from one side of the panel 68 to the other,thus further increasing the thermal efficiency thereof.

A similar effect of not having any straight heat conducting pathstransversely through the insulation panel is incorporated in yet anotherembodiment 55 as shown in FIG. 10. A single spacer sheet 62 is used, buthemispherically-shaped nodules 57 are spaced so that no nodule 57touching outside wall sheet 12 is directly opposite a nodule 57 thattouches inside wall sheet 14. Once again a tortuous path through aseries of "point" contacts, that is, from wall 12 to a nodule 57,through web 66 of sheet 62 to another nodule 57, then to wall 14, isprovided. With chamber 15 between walls 12, 14 highly evacuated, thistortuous path once again provides high thermal efficiency.

Another highly effective insulation panel embodiment 70 according tothis invention is shown in FIGS. 11 through 13. In this embodiment 70,two monolithic spacer sheets 72, 73 are used, each of which has aplurality of elongated ribs 75, 74 separated by webs 77, 76,respectively. These monolithic spacer panels 72, 73 are positioned nextto each other so that the ribs 74 of sheet 72 run perpendicular to theribs 75 of sheet 73. In this manner, the ribs 74 of sheet 72 have linecontacts with outer wall sheet 12. Likewise, the ribs 75 of sheet 75have line contacts with the other outer wall sheet 14. Such linecontacts do make it somewhat more difficult for heat to flow byconduction. Further, the contacts between the ribs 74 on sheet 72 andribs 75 on sheet 73 are essentially "point" contacts, thus almostnegligible heat conductors.

For even higher insulation effectiveness, a plurality of smaller panelsmade as described above, such as any of the embodiments 10, 40, 60, 68,70, can be stacked or laminated together. For example, as shown in FIG.15, a plurality of panels 10 are stacked or laminated together in acomposite panel 80 by embedding them in, or adhering them to, a moreconventional insulation material 82, such as either rigid or flexiblefoam insulation or even a consolidated powder insulation material. Thepanels 10 are preferably staggered with a layer of the conventionalmaterial 82 positioned between each panel 10. This arrangement requiresany heat that traverses the conventional insulation material 82 in thecomposite panel 80 shown in FIG. 15 to travel a tortuous path asindicated by the arrow 94. An R50 or greater insulation value can beprovided with a composite panel 80 only one inch thick. Composite panels80 built with this structure can be easily formed around curves or usedin any shape desired.

A number of means are available for increasing the strength and utilityof panels that are fabricated with the principles of embodiment 10 asshown in FIG. 2. FIGS. 16, 17, 18, 19, and 20 illustrate some of thesemeans.

An embodiment 85 in FIG. 16 is based on the principles of embodiment 10and provides for corrugations in a direction parallel to the X-axis, asillustrated in FIG. 16. Spherical nodules 16 or other glass spacers asdescribed above separate walls 12 and 14, and chamber 15 is highlyevacuated. Welded seal 18 maintains the vacuum. The corrugations keepthe panel 85 rigid in one direction while permitting it to bend inanother direction, as shown in FIG. 17. According to FIG. 16, ifembodiment 85 is generally oriented with the plane formed by the X-Yaxes, then the embodiment is rigid with respect to movement in the X to+Z or X to -Z directions; and flexible with respect to movement in the Yto +Z and Y to -Z directions.

An embodiment 87 according to FIG. 18 is also constructed in accordancewith the general principles of embodiment 10 of FIG. 2 or of otherinsulated panel embodiments as described above. However, in embodiment87, the insulated panel is bent into a cylinder or other enclosingconfiguration in which walls 12, 14 overlap at ends 88, 89, therebyreducing thermal energy loss through welded seams 18. Such ability tobend the panel and overlap ends provides a thermally efficient means ofjoining of ends 88, 89 of embodiment 87 for such uses as wrapping hotwater heaters and other vessels that need to be insulated.

An insulation panel according to the present invention can also beformed in a rippled tube or conduit embodiment 125, as shown incross-section in FIG. 19. The ripples or accordion folds 126 allow thistube or conduit 125 to be curved or bent, as illustrated in FIG. 20, orlongitudinally expanded or contracted, such as to join two immovablerigid conduits 110, as shown in FIG. 21.

A less flexible insulated tube or pipe embodiment 110 shown in FIG. 22has smooth interior and exterior walls 12, 14. Wall 12 forms the outersurface of the insulated pipe, while wall 14 forms the inner conduit113. Separation between walls 12, 14, forming evacuated space 15, isshown in FIG. 22 maintained by helical glass or ceramic spirals 111,112, although other aggregate or monolithic spacer embodiments asdescribed above can also be used to maintain the vacuum space. A veryhigh thermal insulation efficiency in thin-wall tubes or pipes can beprovided for fluids or gasses, including cryogenics, flowing orcontained within conduit 113 with this pipe embodiment 110. The ends oflengths of these insulated pipes 110 can be joined together or toconventional pipes by the rippled connector 125, as described above.When the ends 126, 127 of connector 125 overlap the ends of pipe 110, asshown in FIG. 21, insulation effectiveness is maintained at thesejoints, even if they are welded.

Embodiment 115 according to FIG. 23 comprises two corrugated walls, 12,14, having elongated ribs or protrusions 122 forming valleys 118 andpeaks 119, and a monolithic glass spacer 120, placed between walls 12,14. Walls 12, 14 are joined by welded seam 18. Wall 12 is oriented sothat its ribs 122 form right angles to the ribs of wall 14. Spacer 120separates the valleys 118 of wall 12 and wall 14. The right-angleorientation of the ribs 122 of the respective walls 12, 14 formsessentially very small dimensional (almost point) direct transversecontacts or heat transfer paths through the glass spacer 120 where thevalleys 118 of the respective walls 12, 14 cross each other. In thissense, this embodiment is effectively a structural inverse of theembodiment 70 of FIGS. 11-13 and described above. The chamber 121 formedunder peaks 119 of walls 12, 14 is evacuated. Such an arrangementprovides an insulation panel structure that is very rigid and possessesgreat strength in relation to its weight, while also providing a highdegree of thermal insulation.

Embodiment 130 according to FIG. 25 is similar in concept to embodiment55 of FIG. 10, except that hemispherical nodules 133 are formed on walls12, 14 of embodiment 130. Spacer 134 is a flat plate of monolithic glassor ceramic. Welded seam 18 provides a seal to maintain the vacuum ofevacuated chamber 15. Therefore, the panel 130 is generally thestructural inverse of panel 55 and provides similar advantages andinsulation effectiveness.

Still another embodiment 140 is shown in FIG. 26. Embodiment 140 may beused for thermal-break construction of structural windows. For example,an I-beam or C-channel 141 may provide the basic structural member.Surrounding beam 141 and conforming to its shape are two insulated panelstructures 142, 242, for example, constructed similar to that shown inembodiment 10 of FIG. 2 or according to any of the other suitable panelstructures described above. Thermal break spaces 143, 243 separatestructures 142, 242. Cushion pieces 144, 244 fit snugly againststructures 142, providing a seal and providing for differentialexpansion of glass panes 145, 147, 148. Glass pane 145 is illustrated asan evacuated, fused thermal pane window. Such a typical window can alsobe composed of a plurality of glass panes 147, 148 edge-sealed by asealing structure 146, which may be plastic, metal, or any othersuitable material. Compressible seals 149, 249 assist in preventing airor water leakage. Embodiment 140 thus provides a strong window structurewith a frame structure having highly efficient thermal break propertiesbecause of very long thermal conductance paths.

FIG. 26 illustrates a variation of the insulated window mountingstructure of FIG. 25, wherein thermal pane windows 145 are retained inan I-beam structure 241 by rubber seals 344, 444 between the windows 145and the flanges 451 and 452. The insulation panels 342, 442 of thisembodiment are formed into C-shaped cross-sections that mount onto andcover the exposed surfaces of the respective flanges 451, 452. Eachinsulation panel 342, 442 can be only 0.1 inch (2.5 mm) thick, yet canhave an R15 insulation value. Therefore, both panels 451, 452 togethercan provide very neat appearing--almost imperceptible--R30 insulation onwindow frames 141 and other similar structures that otherwise arevirtually cold shorts across building windows.

The beads 16, spirals 101, or monolithic sheets 62, 72, 73, 120, 134 arepreferably fabricated of glass for applications where temperatures areless than 400° C. for a number of reasons, the most important of whichis the very low outgassing characteristic of glass. Glass also has ahigh compressive strength, mechanical rigidity, low thermalconductivity, and low cost, and it is easy to use in fabrication. Also,glass is essentially opaque to thermal infrared radiation, which, ofcourse, minimizes radiation heat transfer across insulation panels 10,100, 115, 130, particularly where the monolithic spacer sheets 62, 72,73, 120, 134 are used. In applications where temperatures exceed 400°C., the beads 16, spirals 101 or monolithic sheets 62, 72, 73, 120, 134can be fabricated with a ceramic material.

Optical rejection of heat can also be enhanced by includinglow-emissivity coatings 17, 19 of copper, silver, or otherlow-emissivity material, preferably on the interior surfaces of wallsheets 12, 14, 131, 132. Such low-emissivity materials can also becoated on the surfaces of the monolithic spacer sheets themselves,particularly where it is not anticipated that the web 66, 76, 77 orspacers 120, 134 will be broken in a particular application. A metalgetter 21, illustrated in FIG. 2, can also be placed in the chamber 15of any of the panel insulation embodiments described above (although notillustrated in all the figures) prior to evacuating and sealing thechamber 15. The metal getter traps any small amount of reactive gasdesorbed from glass beads or metal walls that may occur during thelifetime of many years duration.

The magnitude of the vacuum and its coordination with the width of thevacuum chamber 15 in all the embodiments described above are important.Low-grade vacuums in the range of 10⁻⁷ atmospheres (10⁻⁴ Torr) areinadequate to contribute much to the thermal transfer resistance orinsulating quality of a panel. The flat line 90 in the graph in FIG. 14illustrates the point that a vacuum does not contribute to any decreasein the rate of thermal transfer across the panel at all until enough ofthe air (or other gases) has been withdrawn to the extent that the meanfree path of a molecule between collisions with other molecules is equalto the spacing or distance between the hot and cold surface. Forultra-thin, high-grade insulation panels as contemplated by thisinvention, at a vacuum of about 10⁻⁴ Torr, the mean free path is equalto the distance between the two wall surfaces, as indicated by the bend92 of the graph in FIG. 14. At that point, thermal conductivity of thepanel 10 decreases, i.e., insulating effectiveness increases, on afairly linear basis in direct relation to a decrease in gas pressure inchamber 15, as indicated by line 94 in FIG. 14. Then, at about 10⁻⁶Torr, a further decrease in pressure does not significantly decreasethermal transfer, because almost all the thermal transfer in that range,indicated by line 96 in FIG. 14, is due to radiation. Therefore, inorder to not only take advantage of a vacuum but also maximize thebeneficial use of a vacuum in this kind of insulation application, it isnecessary to maintain a high-grade vacuum with a pressure in the rangeof 10⁻⁶ Torr or lower.

For purposes of illustration, the ultra-thin insulation panels accordingto this invention can be fabricated very effectively and used verybeneficially in overall thickness in the range of about 0.1 inch (2.5mm). The metal wall sheets can be 0.005 to 0.010 inch (0.2 to 0.3 mm)thick, and the spacers can be about 0.08 inch (2 mm). The monolithicglass inserts 62, 72, 73 can be thin, rolled glass sheets with regularlyspaced spherical nodules 64 or ribs 74, 75. Gas-phase conduction isnearly eliminated by sealing the chamber 15 under a high-grade vacuumwith a pressure of only 10⁻⁵ Torr and preferably 10⁻⁶ Torr or less, asillustrated by FIG. 14 and discussed above. Solid-phase conduction isminimized by the use of low thermal conductivity material, such asglass, for mechanical side wall supports or spacers and by the use ofnearly "point" contacts between the supports and the wall sheets, asdescribed above in relation to the specific structures and embodimentsillustrated. A 0.1-inch (2.5 mm) thick insulation panel, as describedabove, can have an insulation value as high as R15 i.e., R=15° F. - hr.ft² /BTU, which resists thermal transfer as well as a 21/2 -inch thicksection of polymer foam or nearly seven inches of standard-densityfiberglass.

By way of illustration, and not of limitation, the following is providedto illustrate the advantages of the ultra-thin Compact Vacuum Insulation(CVI) embodiments of the present invention due to such items as itscompactness, effective working temperatures, light weight, and reductionin the use of chlorofluorocarbons (CFC).

In many applications a premium is paid for volume, and ahigh-performance insulation material occupying less volume is thereforemore valuable. An indicator of these applications is provided by thegrowing substitution of more-expensive expanded foam products withR-values of 5 to 10 per inch, or other exotic insulations, forless-expensive bulk insulations such as fiberglass, rockwool andcellulose, with R-values of 2 to 4 per inch. Such applications include:refrigerators; freezers; display case shells for chilled products suchas meat, produce, flower, and liquor; refrigerated intermodal transportcontainers; and refrigerated trucks and trailers, tank, and rail cars;steam and hot and cold water piping; district heating and coolingpiping; industrial process hot and cold storage tanks or containers;industrial hot and cold process equipment; automobile, train, plane andship body shells; building HVAC equipment and ducts; roofs, walls, andfloors of buildings; chilled computer circuits and components; diurnaland annual cycle storage tanks; portable hot and cold storage andtransport containers; thermal isolation of heat-producing producingcomputer components and other operations; and temperature maintenance ofhigh temperature processes such as sodium-sulfur batteries andheat-retention diesels.

The ultra-thin CVI insulation panels and conduits according to thisinvention as described above are just as effective in cryogenic process,transport, and storage situations as the thicker, more complex,state-of-the-art cryopumped insulation, where a layered multifoilinsulation is continuously vacuum-pumped by thermal absorption by theextremely cold material itself. However, since the ultra-thin CVIinsulation panels and conduits of the present invention do not rely onsuch cryopumping to maintain their insulation effectiveness, they do notrequire such energy input or waste. In further contrast, this insulationaccording to the present invention is also just as effective in ambientand high-temperature applications as it is in low-temperatureapplications, whereas cryopumped insulation works only at extremely lowtemperatures, and the ultra-thin CVI of the present invention is muchless bulky and more flexible than cryopumped insulation.

Related to this cryogenic application is the case of high-temperaturesuperconductors. As long as superconductivity took place only atcryogenic temperatures, transmission of electricity was through circuitsthat cryo-pumped their multifoil insulating jackets. Such energy draindue to cryopumping the insulation could be substantial when cryopumpinggreat lengths of superconductor circuit. Such energy drain could beavoided with the ultra-thin

CVI insulation of the present invention, as discussed above. Equally asimportant, however, is the current on-going development ofsuperconductors that operate above cryogenic temperatures, yet stillneed effective insulation. Since cryopumping does not occur at highertemperatures, the ultra-thin CVI insulation of this invention may be theonly currently available practical alternative.

Benefits of the relatively lighter weight of the embodiments of thepresent invention over prior art insulating materials and techniquesinclude: lighter-weight, less-expensive machinery is required forfabrication and handling; lighter-weight fasteners are required forattachment to other structures; lighter-weight structures are requiredto hold the present invention; and less fuel and effort is required totransport the embodiments, fasteners, and accompanying structure, ifany, to which it is attached or upon which it rests.

By way of further example, existing and prospective insulation productsare compared to an embodiment of the present (CVI) invention in thefollowing table:

    __________________________________________________________________________    APPROXIMATE VALUES FOR PROTOTYPICAL 17 CUBIC FOOT                             REFRIGERATOR/FREEZER                                                                                   Weight (lb)                                                                         Volume (ft.sup.3)                              Type of Insulation       of R15                                                                              of R15                                         (R per inch) lbs/ft.sup.3                                                                       lbs/R15/ft.sup.2                                                                     Insulation                                                                          Insulation                                     __________________________________________________________________________    Loose-fill fiberglass (R3)                                                                  2   0.83   35.3  17.50                                          Polyurethane foam (R7)                                                                      2   0.35   14.9   7.70                                          Perlite powder                                                                             14   7.00   297.5 21.30                                          (in atm. R2.5)                                                                Optimized mixed powder                                                                     15   0.97   41.2  21.30                                          (at 0.1 mm Hg, R20)                                                           CVI (at 10.sup.-6 torr)                                                                    N/A  0.60   24.0   0.35                                          __________________________________________________________________________

Another advantage of the advanced insulation according to this inventionis provided by the growing body of evidence that a chemical constituentof the best low-cost insulations currently available, i.e., the expandedpolymer foams, is damaging the earth's protective ozone layer. The (CFC)used to "Blow" (or expand) the foam escapes from the foam over time,gradually rising to the stratosphere where, over a 50-year life, it actsas a catalyst in the destruction of 50,000 times its weight of ozone.

Besides the present invention being a direct substitute in manyapplications for CRC-blown insulating foams, its other attributes oflight weight, compactness, non-flammability, non-toxicity, low-cost,etc., make it beneficial to increase the R-values presently utilized inappliances and other applications, as well as those now being proposed.In the many cases where the thermal envelope is enclosing spaces ofproducts chilled by standard vapor-compression equipment with CFCworking fluid, or refrigerant, the present invention allows for adown-sizing of the vapor compression equipment, and a resultingreduction in the amount of CFC refrigerant, as well as energy, needed toachieve and maintain the desired cool or chilled temperatures in theenclosed spaces. With the reduction o in compression equipment combinedwith replacement of CFCS-emitting materials with CVI as insulation,refrigeration equipment and other CFC insulation methods can beeliminated as a major source of CFC pollution.

A further advantage of the embodiments of this invention havingcorrugated designs is to enhance the ability to bend the CVI in thedirection normal to the direction of the corrugated ribs as shown inFIGS. 16 and 17 and described above. This corrugated configurationallows easy forming of the insulation panel around cylindrical tanks.The corrugation also reduces contact with a rigid, non-corrugatedexterior or interior surface to essentially a number of line contacts,which further thermally isolates the object being insulated. In the caseof insulated piping or ducting, such corrugated insulation panels willallow bending of the piping or ducting while maintaining a very strong"hoop strength" design against collapse.

Another application for the ultra-thin compact vacuum insulation isrelated to the recent improvements in glazings. From an R-value of about1 for single glazing, and about 2 for standard double glazing, designsand prototypes have appeared within the last 5 years for advancedglazings with R-values of 3 to 10. One result of these advances is thatmore attention has been focused on the window frame itself, which canaccount for as much as 30% of the total fenestration "rough opening" ina building envelope, yet is often essentially a cold short between theinterior and the exterior of the building. Wood and vinyl-clad woodframes are modest improvements, with maximum total R-values approaching5. However, considering the effect of the window frames on R-valueintegrated over the entire fenestration area, much more improvementwould be beneficial. The ultra-thin compact vacuum insulation panelwindow frame coverings or caps 142, 242 shown in FIG. 25 and 342, 442shown in FIG. 26 and described above can achieve R30 insulation valueswhen installed on both the interior and exterior sides of the windowframe, and R15 when installed on only one side with as little as 0.1inch (2.5 mm) panel thickness.

The table below compares the effects of frames of different R-values onthe integrated R-value of the fenestration opening.

    ______________________________________                                        Integrated R-values for 10 ft.sup.2 Window                                                Frame R-value                                                     Glazing R-Value                                                                           (30% Coverage)                                                    (70% Coverage)                                                                            1     2       4   8      16   32                                  ______________________________________                                        1           1.0   1.2     1.3 1.4    1.4  1.4                                 2           1.5   2.0     2.4 2.6    2.7  2.8                                 4           2.1   3.1     4.0 4.7    5.2  5.4                                 8           2.6   4.3     6.3 8.0    9.7  10.6                                16          2.9   5.2     8.5 12.5   16.0 19.6                                ______________________________________                                    

The foregoing description is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and processesshown as described above. Accordingly, all suitable modifications andequivalents may be resorted to falling within the scope of the inventionas defined by the claims which follow.

The embodiments of the invention in which an exclusive property ofprivilege is claimed are defined as follows:
 1. Thermal insulatingapparatus, comprising:a plurality of thermal insulating panels, each ofwhich has two closely spaced-apart metallic wall panels with spacerstherebetween bridging the two wall panels, such spacers being shapedsuch that thermal conduction through the spacer sheets must be throughnear "point" contacts of solid materials, the edges of said wall panelsbeing welded together to form a chamber therebetween, and said chamberbeing evacuated to a high-grade vacuum having a pressure at least as lowas 10⁻⁵ Torr; a large, conventional-type insulation substrate havingsaid thermal insulating panels attached thereto in at least two layersin such a manner that a layer of foam-type insulating intercedes betweenthe layers of thermal insulating panels as well as between adjacent onesof said thermal insulating panels in each layer, and wherein saidinsulating panels in one of said layers are staggered with respect tothe insulating panels in adjacent ones of said layers such that heatconducted through said substrate must travel in a tortuous path throughthe foam-type insulation between adjacent layers and between saidinsulating panels in said layers.
 2. Composite thermal insulation,comprising:a first plurality of thin, evacuated insulation panels withperipheral edges positioned in adjacent, but spaced-apart relation to,each other in a substantially common first planar alignment with aspaced distance between respective peripheral edges of adjacent ones ofsaid evacuated panels in said first planar alignment; a second pluralityof thin, evacuated insulation panels with peripheral edges positioned inadjacent, but spaced-apart relation to, each other in a substantiallycommon second planar alignment with a spaced distance between respectiveperipheral edges of adjacent ones of said evacuated panels in saidsecond planar alignment, said second planar alignment being positionedadjacent, but in substantially parallel, spaced-apart relation to, saidfirst parallel alignment such that there is a spaced distance betweensaid first and second planar alignments, and the panels in said firstplanar alignment being staggered with respect to the panels in saidsecond planar alignment such that at least one of said panels intersectsany line that is perpendicular to said first and second planaralignments; and a mass of different thermal insulation materialsubstantially filling said spaced distances between said respectiveperipheral edges as well as substantially filling said spaced distancebetween said first and second planar alignments.
 3. The compositethermal insulation of claim 2, wherein said different insulationmaterial is a foam insulation material.
 4. The composite thermalinsulation of claim 2, wherein said different insulation material is apowder insulation material.